As a marketing vehicle to survive in intensified retailing competition, retailer brand development has been adopted by retailers in Korea. As evidence, the retailer brand share of a major retailer, Tesco Korea, has grown from 20% in 2007 to 22.8% in the first half of 2008. It means that retailers have provided more and more retailer brand foods for customers. With the growing accessibility to retailer brand foods, it would be expected that the number of retailer brand food claims will increase. Customers have increasingly exposed to a variety of marketing activities conducted by retailers. When buying the retailer brand foods, customers tend to be affected by marketing activities of retailers. Despite the fact that customers trust retailers and then, buy their brand foods, in case of food accidents caused by production process, customers have to seek compensation from a retailer brand supplier. Of course, a retailer tends to shift its responsibility to its suppliers. Accordingly, it is not easy for customers to solve food claims. The research, therefore, aims at exploring the relationship between the buying-decision processes of retailer brand customers and which side takes legal responsibility for food claims. To effectively achieve the research aim, the author adopted a quantitative and a qualitative research technique, in order to supplement the disadvantages of each method. Before field research, based on the developed research model, the author pre-tested questionnaire with 10 samples, amended, and handed out to 400 samples. Amongst them, 316 questionnaires are available. For a focus group interview, 9 participants were recruited, who are students, housewives, and full-time workers, aged from 20s to 40s. Through the focus group interview as well as the questionnaire results, it was found that most customers were influenced by a retailer or store image in a customer's mind, retailer reputation and promotional activities. Surprisingly, customers think that the name of a retailer is a more important factor than who produces retailer brand foods, even though many customers check a retailer brand supplier, when making a buying-decision. Rather than retailer brand suppliers, customers trust retailers. That is why they purchase retailer brands. Nevertheless, production-related food claims is not involved with retailers. In fact, it would be difficult for customers to distinguish whether a food claim is related to selling or manufacturing processes. Based on research results, from a customer perspective, the research suggests that the government should require retailers to take the whole responsibility for retailer brand food claims, preventing retailers from passing the buck to retailer brand suppliers. In case of food claims, in order for customers to easily get the compensation, it is necessary to reconsider the current system. If so, retailers have to fully get involved in retailer brand production stage, and further, the customer awareness of retailer brands will be improved than ever before. Retailers cannot help taking care of the whole processes of retailer brand development, because of responsibility. As a result, the process to seek compensation for food claims might become easier, and further, the protection of customer right might be improved.